Fabricated labyrinth seal structure

ABSTRACT

Inherent flexibility is incorporated in a labyrinth seal structure for a rotatable member by providing a relatively thin arcuately segmented corrugated metal sheet having honeycomb metal seals secured to the ridges of the corrugated metal sheet, thereby precluding the need for the spring-backed grooved seal rings previously utilized in labyrinth seals.

Ilnited States Patent [191 Adelizzi I FABRICATED LABYRINTH SEALSTRUCTURE [75] Inventor: Richard S. Adelizzi, Marlton, NJ.

[73] Assignee: Westinghouse Electric Corp., Pittsburgh, Pa.

221' Filed: Jan.2l, 1971 211 Appl.No.: 108,428

[52] U.S.Cl ..277/53,415/174 51 Int. Cl. ..F02f 11/00, FOld 11/08 [58]Field of Search...416/174; 277/53, 55,56, 96 R; 415/174 [5 6] ReferencesCited UNITED STATES PATENTS 3,503,616 3 1970 Hickey 2,886,351 5/1950Heard 12/1960 Bobo ..416/174 lMarcl1 13, 1973 3,501,089 3/1970 Alford..277/53 3,038,730 6/1962 Bentley ....277/53 X 3,317,254 5/1967Sattertwaite ..416/174 FOREIGN PATENTS OR APPLICATIONS 840,573 7/1960Great Britain ..277/55 Primary ExaminerSamuel B. Rothberg Att0rneyA. T.Stratton, F. P. Lyle and F..Cristiano, Jr,

[57] ABSTRACT Inherent flexibility is incorporated in a labyrinth sealstructure for a rotatable member by providing a relatively thinarcuately segmented corrugated metal sheet having honeycomb metal sealssecured to the ridges of the corrugated metal sheet, thereby precludingthe need for the spring-backed grooved seal rings previously utilized inlabyrinth seals.

4 Claims, 3 Drawing Figures FABRICATED LABYRINTH SEAL STRUCTUREBACKGROUND OF THE INVENTION This invention relates, generally, to sealsfor controlling leakage of a fluid around a rotatable member and, moreparticularly, to seals of the labyrinth type.

Heretofore, labyrinth seals have usually included arcuately segmentedgrooved metal rings mounted around a rotatable member, such as a shaft,having grooves therein corresponding to the grooves in the seal rings.Lead springs have been provided to maintain the ring segments inposition and to permit misalignment of the shaft without excessiverubbing of the seal members.

SUMMARY OF THE INVENTION In accordance with one embodiment of theinvention, a labyrinth seal for rotatable member, such as a shaft, isconstructed of relatively thin arcuately segmented corrugated sheetmetal having arcuate segments of a honeycomb metal seal welded to theridges of the corrugations. Each side edge of each corrugated sheetsegment has a portion which extends axially and then radially withanother axially extending portion welded to a back-up member to provideinherent flexibility in the seal structure without utilizing back-upsprings. The honeycomb metal seals are installed with a small clearancebetween the seals and the rotatable member, thereby obtaining minimumleakage around the rotatable member.

BRIEF DESCRIPTION OF THE DRAWING For a better understanding of thenature of the invention, reference may be had to the following detaileddescription, taken in conjunction with the accompanying drawing, inwhich:

FIG. 1 is a view, partly in side elevation and partly in section, of aportion of a steam turbine including a gland case having a labyrinthseal structure therein constructed in accordance with the prior art;

FIG. 2 is a view, in secton, of a portion of a gland case similar tothat shown in FIG. 1 and having a labyrinth seal structure thereinconstructed in accordance with the present invention, and

FIG. 3 is a view, in section, of a portion of a gas turbine having alabyrinth seal structure therein also constructed in accordance with thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 of the drawing, thereis shown a labyrinth seal structure constructed in accordance with theprior art. As described in U.S. Pat. No. 3,503,616 issued Mar. 31, 1970to Herbert A. Hickey and assigned to the same assignee asthe presentapplication, the portion of a turbine structure shown in FIG. 1comprises a shaft 110 rotatably mounted in a main housing 11 which isdivided along a horizontal plane P-P into an upper portion 12 and alower portion 13. The shaft is supported in suitable bearings (notshown).

In order to reduce steam leakage around the shaft Ill, arcuatelysegmented seal rings 14 of the labyrinth type are mounted around theshaft 10 in the main housing ill and also in a gland case 15 which isremovably attached to the end of the main housing 11 by bolts l6.

The gland case 15 is also divided along a horizontal plane into an upperportion 17 and a lower portion 18. As described in the aforesaid patent,each segmented gland ring 14 is divided along a horizontal plane into anupper portion and a lower portion. The two halves of the gland case 15are bolted together by bolts 21. Likewise, the two halves of the mainhousing 1 1 may be bolted together by bolts (not shown).

As shown in FIG. 1, each gland ring 14 has a plurality of ridges 23thereon which extend into grooves 24 on the shaft 10, thereby providinga shaft seal of the labyrinth type. A leaf spring 25 is provided betweeneach segment of the seal ring 14 and the gland case 15. The springs 25hold the segmented seal ring 14 into position when there is no pressurein the gland case 15 and allow the segments of the seal ring 14 to moveradially outwardly when rubbing with the shaft occurs due tomisalignment of the shaft.

A labyrinth seal constructed in accordance with the prior art requiresexpensive machining of the seal ring segments and the shaft. Aspreviously explained, backup springs are required between the seal ringsegments and the enclosing casing. Furthermore, the seal ring segmentshave usually been composed of bronze, thereby requiring provision for alarger thermal expansion between the bronze seals and the casing.

In order to provide a more efficient and less expensive seal, thelabyrinth seal structure shown in FIG. 2 has been devised. In thestructure shown in FIG. 2, the shaft 10 is rotatably mounted in ahousing 11 having a gland case attached to one end of the housing bymeans of bolts 16. The shaft 10 extends through the main housing 11 andthe gland case 15a. The labyrinth seal structure comprises generallycylindrical arcuately segmented back-up members 26 having T-shapedportions 27 thereon slidably disposed in T-shaped grooves 28 in thecasing 151;.

A relatively thin generally cylindrical arcuately segmented corrugatedmetal sheet 30 is secured to each segment of each back-up member 26, asby welding. Arcuately segmented seal rings 31 are secured to ridges 32of the corrugated metal sheets 30. As shown more clearly in the righthand portion of FIG. 2, the seal rings 31 may be of a cellular structurecomposed of a honeycomb metal, or other suitable material, and they aredisposed in close proximity to the shaft 10, thereby minimizing leakagearound the shaft. The corrugated sheets 30 are preferably composed ofsteel, thereby precluding the need for the large thermal expansionallowance previously required between bronze seals and the backingpiece.

In order to provide flexiblity in the seal structure, each side edge ofeach segment of the corrugated sheet 30 has an axially extending portion33, a radially extending portion 34 and another axially extendingportion 35 which is secured to the back-up member 26, as by welding,thereby spacing the sheet 30 from the back-up member. Thus, ifmisalignment of the shaft occurs, the seal structure will flex atsection AA to BB, and at similar sections on opposite sides, to takecare of the misalignment without excessive rubbing between the sealrings 31 and the shaft 10. Therefore, back-up springs are not requiredin the present seal structure.

In the embodiment of the invention shown in FIG. 3, the labyrinth sealstructure is utilized in conjunction with a structure for cooling theroot portions of gas turbine rotor blades, such as described in acopending application Ser. No. 791,892, filed Jan. 17, 1969, now US.Pat. No. 3,572,966, by James Howard Borden and Augustine Joseph Scalzoand assigned to the same assignee as the present application. Thestructure shown comprises a rotatable tubular member 36 encompassing andspaced from a torque tube 37 to provide an air passageway 38 between themember 36 and the tube 37. The torque tube 37 surrounds stay bolts 39which extend through the torque tube to the rotor of a compressor (notshown). Air from the compressor is delivered to the turbine rotor discs,(not shown) through the passageway 38 as indicated by the arrows.

The labyrinth seal structure is similar to the one previously described.Back-up members 26a are mounted in the turbine stator structure in anysuitable manner. The segmented corrugated metal sheets 30 are secured tothe segmented annular back-up members 26a in the manner hereinbeforedescribed to provide inherent flexibility in the seal structure. Aspreviously described, the seal structure is segmented with minimum widthgaps between segments to permit thermal expansion of the structure.

From the foregoing description, it is apparent that the inventionprovides a labyrinth seal structure having inherent fiexiblity. A moreefficient sealing device than prior devices is provided since thepresent structure can maintain closer radial clearance, as the rotatablemember of the seal arrangement can be relied on to set the minimumclearance required. The present structure is relatively low in cost.There is a relatively high reduction in the cost of the seals alone, ascompared with prior labyrinth seal structures. An even greater costsavings is effected since a more efficient seal is provided, therebyrequiring less seals and a shorter machine.

I claim as my invention:

1. A labyrinth seal structure for a rotatable member, said sealstructure comprising a generally cylindrical back-up member spaced fromand encircling the rotatable member, a relatively thin, generallycylindrical, corrugated sheet metal member encircling the rotatablemember within the back-up member and being attached to the back-upmember at the ends of the sheet metal member, the corrugations of saidsheet metal member extending circumferentially to form a plurality ofcircular, substantially parallel ridges spaced apart axially of thesheet metal member, and seal rings secured to said ridges in closeproximity to the rotatable member.

2. A labyrinth seal as defined in claim 1 in which said seal rings aremade of honeycomb metal.

3. A labyrinth seal as defined in claim 1 in which said sheet metalmember has sufficient flexibility to compensate for misalignment.

4. A labyrinth seal as defined in claim 3 in which said seal rings aremade of honeycomb metal.

1. A labyrinth seal structure for a rotatable member, said sealstructure comprising a generally cylindrical back-up member spaced fromand encircling the rotatable member, a relatively thin, generallycylindrical, corrugated sheet metal member encircling the rotatablemember within the back-up member and being attached to the back-upmember at the ends of the sheet metal member, the corrugations of saidsheet metal member extending circumferentially to form a plurality ofcircular, substantially parallel ridges spaced apart axially of thesheet metal member, and seal rings secured to said ridges in closeproximity to the rotatable member.
 1. A labyrinth seal structure for arotatable member, said seal structure comprising a generally cylindricalback-up member spaced from and encircling the rotatable member, arelatively thin, generally cylindrical, corrugated sheet metal memberencircling the rotatable member within the back-up member and beingattached to the back-up member at the ends of the sheet metal member,the corrugations of said sheet metal member extending circumferentiallyto form a plurality of circular, substantially parallel ridges spacedapart axially of the sheet metal member, and seal rings secured to saidridges in close proximity to the rotatable member.
 2. A labyrinth sealas defined in claim 1 in which said seal rings are made of honeycombmetal.
 3. A labyrinth seal as defined in claim 1 in which said sheetmetal member has sufficient flexibility to compensate for misalignment.